Seem incensed by the restraint (6)
I believe the answer is:
bridle
'the restraint' is the definition.
(bridle is a kind of restraint)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for bridle that I've seen before include "Check" , "Bristle" , "Horse restraint" , "Become indignant" , "Bit and reins, etc" .)